scholarly journals Appendix A: Effect of Detector Attenuation Change and Chart Speed on Peak Height, Peak Width, and Peak Area

2004 ◽  
pp. 989-993
Author(s):  
Robert L. Grob ◽  
Eugene F. Barry
Keyword(s):  
Peak Height ◽  
Peak Width ◽  
Chart Speed

Generation of Synthetic Background Spectra by Filtering the Sample Interferogram in FT-IR

1998 ◽  
Vol 52 (3) ◽  
pp. 375-379 ◽  
Author(s):  
Luis H. Espinoza ◽  
Thomas M. Niemczyk ◽  
Brian R. Stallard
Keyword(s):  
Peak Height ◽  
Peak Width ◽  
Absorbance Spectrum ◽  
Background Spectrum ◽  
Filtering Method ◽  
Generation Technique ◽  
Sample Spectrum ◽  
Ft Ir ◽  
Gaseous Sample

The calculation of an absorbance spectrum depends on the measurement of a blank, or background spectrum. In many cases, such as the determination of atmospheric constituents with the use of open-path Fourier transform infrared spectroscopy (FT-IR) or the determination of water vapor in a gaseous sample, it is very difficult to obtain a good background spectrum. The difficulty is due to the fact that it is nearly impossible in these situations to measure a spectrum with no analyte features present. We present a method of generating a background spectrum based on filtering the analyte features from the sample spectrum. When the filtering method is used, the accuracy of the results obtained is found to be dependent upon the analyte peak width, peak height, and type of filter employed. Guidelines for the use of this background generation technique for quantitative determinations are presented.

scholarly journals Impact of white-mater mask selection on DTI histogram-based metrics as potential biomarkers in cerebral small vessel disease

2021 ◽  
Author(s):  
Ana R Fouto ◽  
Rita G. Nunes ◽  
Joana Pinto ◽  
Luísa Alves ◽  
Sofia Calado ◽  
...  
Keyword(s):  
Executive Function ◽  
White Matter ◽  
Small Vessel Disease ◽  
Peak Height ◽  
Cerebral Small Vessel Disease ◽  
Small Vessel ◽  
Peak Width ◽  
Vessel Disease ◽  
The Impact ◽  
Potential Biomarkers

Abstract Purpose Histogram-based metrics extracted from diffusion-tensor imaging (DTI) have been suggested as potential biomarkers for cerebral small vessel disease (SVD), but methods and results have varied across studies. This work aims to assess the impact of mask selection for extracting histogram-based metrics of fractional anisotropy (FA) and mean diffusivity (MD) on their sensitivity as SVD biomarkers.Methods DTI data were collected from 17 SVD patients and 12 healthy controls. For each participant, FA and MD maps were estimated; from these, histograms were computed on two alternative whole-brain white-matter masks: normal-appearing white-matter (NAWM) and mean FA tract skeleton (TBSS). Histogram-based metrics (median, peak height, peak width, peak value) were extracted from the FA and MD maps. These were compared between patients and controls, and correlated with the patients’ cognitive scores (executive function and processing speed).Results White matter mask selection significantly impacted FA and MD histogram metrics and affected their ability to discriminate between groups. Moreover, we observed that the mask can influence the correlations with cognitive measures. Nevertheless, the MD peak height and MD peak width metrics remained significantly correlated with executive function, regardless of the mask.Conclusion Our results corroborate previous reports and further support the value of DTI histogram-based metrics as SVD biomarkers. However, they also highlight the importance of the processing methodology, in particular the choice of white matter mask, as hence the urgent need to mitigate the lack of standardized MRI data-processing pipelines.

Analysis of Resistance Asymmetry Due to p-n Junctions in Graphene FETs

2010 ◽  
Vol 1259 ◽  
Author(s):  
Kangmu Lee ◽  
Lingquan Wang ◽  
Peter Asbeck ◽  
Jeong Moon
Keyword(s):  
Electric Field ◽  
Carrier Concentration ◽  
Peak Height ◽  
Threshold Condition ◽  
Gate Bias ◽  
Peak Width ◽  
Carrier Distribution ◽  
Back Gate ◽  
Additional Resistance ◽  
Channel Region

AbstractFor graphene FETs, asymmetry in the drain current transfer characteristics has been observed. It has been proposed that asymmetry is due to additional resistances from p-n transition regions along the channel [1,2]. Calculations of the additional resistance have been received attention for small p-n transition lengths [3,4]. In this paper, we analyze the resistance of graphene FETs with p-n junctions when transition lengths are long compared with energy and momentum relaxation lengths, as is found in many experimental FETs. We employ a two dimensional device simulator to determine the electric field and channel conductivity variations in the vicinity of the FET gate, assuming rapid electron/hole equilibration. The simulations show added resistances in the range of 50-500 Ω μm p-n junction. We also extract the additional p-n resistance ΔR from experimental results by plots of Vd/Id vs. 1/|Vg-Vt|. Values of ΔR of order 450 Ω μm were extracted from FET results reported in [2]. Epitaxial graphene FETs fabricated on a SiC substrate [5] gives additional resistance of 620 Ωum. Both results are in reasonable agreement with the simulations.The physically-based device simulator Atlas of Silvaco with parameters modified for graphene was used to obtain carrier distributions. A graphene FET on SiO2 substrate with a global back gate and 0.3μm gate/drain and gate/source gaps was studied. The carrier density in the gap region was controlled by back gate bias (Vbg) while the channel region under the top gate was modulated by top and back gate simultaneously. A long channel device at Vds=10mV was used to minimize the lateral electric field effect.From the simulated carrier distribution, we can obtain the resistivity along the channel by ρ=1/[qμ(n+p)]. Mobility is assumed to be equal for electrons and holes, and depends on carrier concentration Ns, μ=μ0 (N0/Ns)1/2 where N0 and μ0 are intrinsic carrier concentration and peak mobility, respectively. Under positive Vbg, the graphene layer becomes n-type in the gap region and channel region. Proper top gate bias (Vg) may be applied to make channel region intrinsic, p-type or n-type. Therefore, various configurations along the channel such as npn or nnn structures may be created. In the p-n transition region, the total number of carriers reduces to N0 and resistivity shows a peak. The additional resistance of a p-n junction can be calculated by integrating the difference of the resistivity vs. channel position for the nnn and npn structures. The integrated resistance value is impacted by the peak height and peak width. The peak height is controlled by Vg-Vt; the resistivity reaches a maximum at the threshold condition, where the electron and hole densities reach their intrinsic levels. The peak width is also controlled by Vg, via fringing field of the gate.

Organic chemistry students’ interpretations of the surface features of reaction coordinate diagrams

2018 ◽  
Vol 19 (3) ◽  
pp. 919-931 ◽  
Author(s):  
Maia Popova ◽  
Stacey Lowery Bretz
Keyword(s):  
Organic Chemistry ◽  
Qualitative Study ◽  
Chemical Reactions ◽  
Chemical Species ◽  
Peak Height ◽  
Reaction Coordinate ◽  
Peak Width ◽  
Structured Interviews ◽  
Surface Features ◽  
Chemistry Students

Organic chemistry students struggle with understanding the energetics of chemical reactions. Reaction coordinate diagrams are one tool that is widely used in organic chemistry classrooms to assist students with visualizing and explaining the energy changes that take place throughout a reaction. Thirty-six students enrolled in organic chemistry II participated in a qualitative study that used semi-structured interviews to investigate the extent to which students meaningfully extract and integrate information encoded in reaction coordinate diagrams. Results show that students have difficulties explaining the meanings of surface features such as peaks, valleys, peak height, and peak width. Analysis of students’ explanations resulted in four themes that describe students’ challenges with correctly interpreting the features of reaction coordinate diagrams. Students conflated transition states and intermediates, despite being able to recite definitions. Students described the chemical species encoded at points along thex-axis of the reaction coordinate diagrams, while largely ignoring the energies of the species encoded along they-axis. Implications for teaching organic chemistry are discussed.

Valence electron spectroscopy of inhomogeneous media

1992 ◽  
Vol 50 (2) ◽  
pp. 1150-1151
Author(s):  
A. Howie ◽  
D.W. McComb
Keyword(s):  
Specific Gravity ◽  
Loss Function ◽  
Electron Spectroscopy ◽  
Valence Electron ◽  
Peak Height ◽  
Loss Functions ◽  
Loss Peak ◽  
High Energies ◽  
Valence Electron Density ◽  
Electron Microscopist

The bulk loss function Im(-l/ε (ω)), a well established tool for the interpretation of valence loss spectra, is being progressively adapted to the wide variety of inhomogeneous samples of interest to the electron microscopist. Proportionality between n, the local valence electron density, and ε-1 (Sellmeyer's equation) has sometimes been assumed but may not be valid even in homogeneous samples. Figs. 1 and 2 show the experimentally measured bulk loss functions for three pure silicates of different specific gravity ρ - quartz (ρ = 2.66), coesite (ρ = 2.93) and a zeolite (ρ = 1.79). Clearly, despite the substantial differences in density, the shift of the prominent loss peak is very small and far less than that predicted by scaling e for quartz with Sellmeyer's equation or even the somewhat smaller shift given by the Clausius-Mossotti (CM) relation which assumes proportionality between n (or ρ in this case) and (ε - 1)/(ε + 2). Both theories overestimate the rise in the peak height for coesite and underestimate the increase at high energies.

Thrombin generation in paediatric patients with congenital heart disease

2008 ◽  
Vol 28 (S 01) ◽  
pp. S61-S66 ◽  
Author(s):  
G. Cvirn ◽  
A. Rosenkranz ◽  
B. Leschnik ◽  
W. Raith ◽  
W. Muntean ◽  
...  
Keyword(s):  
Congenital Heart Disease ◽  
Heart Disease ◽  
Negative Correlation ◽  
Congenital Heart ◽  
Thrombin Generation ◽  
Significant Negative Correlation ◽  
Peak Height ◽  
Global Test ◽  
Paediatric Patients ◽  
Age Range

SummaryThrombin generation was studied in paediatric patients with congenital heart disease (CHD) undergoing cardiac surgery using the calibrated automated thrombography (CAT) in terms of the lag time until the onset of thrombin formation, time to thrombin peak maximum (TTP), endogenous thrombin potential (ETP), and thrombin peak height. The suitability to determine the coagulation status of these patients was investigated. Patients, material, methods: CAT data of 40 patients with CHD (age range from newborn to 18 years) were compared to data using standard coagulation parameters such as prothrombin (FII), antithrombin (AT), tissue factor pathway inhibitor (TFPI), prothrombin fragment 1.2 (F 1.2), thrombin-antithrombin (TAT), activated partial thromboplastin time (aPTT), and prothrombin time (PT). Results: A significant positive correlation was seen between ETP and FII (p < 0.01; r = 0.369), as well as between peak height and F II (p < 0.01; r = 0.483). A significant negative correlation was seen between ETP and TFPI values (p < 0.05; r = –0.225) while no significant correlation was seen between peak height and TFPI. A significant negative correlation was seen between F 1.2 generation and ETP (p < 0.05; r = –0.254) and between F 1.2 generation and peak height (p < 0.05; r = –0.236). No correlation was seen between AT and ETP or peak. Conclusions: CAT is a good global test reflecting procoagulatory and inhibitory factors of the haemostatic system in paediatric patients with CHD.

Validated Stability Indicating HPTLC Method for the Estimation of Amoxapine in Different Stress Conditions

2019 ◽  
Vol 15 (3) ◽  
pp. 273-279
Author(s):  
Shweta G. Rangari ◽  
Nishikant A. Raut ◽  
Pradip W. Dhore
Keyword(s):  
High Performance ◽  
Limit Of Detection ◽  
Degradation Products ◽  
Analysis Data ◽  
Peak Height ◽  
Good Resolution ◽  
Stability Indicating ◽  
Limit Of Quantitation ◽  
Wide Range ◽  
Hptlc Method

Background:The unstable and/or toxic degradation products may form due to degradation of drug which results into loss of therapeutic activity and lead to life threatening condition. Hence, it is important to establish the stability characteristics of drug in various conditions such as in temperature, light, oxidising agent and susceptibility across a wide range of pH values.Introduction:The aim of the proposed study was to develop simple, sensitive and economic stability indicating high performance thin layer chromatography (HPTLC) method for the quantification of Amoxapine in the presence of degradation products.Methods:Amoxapine and its degraded products were separated on precoated silica gel 60F254 TLC plates by using mobile phase comprising of methanol: toluene: ammonium acetate (6:3:1, v/v/v). The densitometric evaluation was carried out at 320 nm in reflectance/absorbance mode. The degradation products obtained as per ICH guidelines under acidic, basic and oxidative conditions have different Rf values 0.12, 0.26 and 0.6 indicating good resolution from each other and pure drug with Rf: 0.47. Amoxapine was found to be stable under neutral, thermal and photo conditions.Results:The method was validated as per ICH Q2 (R1) guidelines in terms of accuracy, precision, ruggedness, robustness and linearity. A good linear relationship between concentration and response (peak area and peak height) over the range of 80 ng/spot to 720 ng/spot was observed from regression analysis data showing correlation coefficient 0.991 and 0.994 for area and height, respectively. The limit of detection (LOD) and limit of quantitation (LOQ) for area were found to be 1.176 ng/mL and 3.565 ng/mL, whereas for height, 50.063 ng/mL and 151.707 ng/mL respectively.Conclusion:The statistical analysis confirmed the accuracy, precision and selectivity of the proposed method which can be effectively used for the analysis of amoxapine in the presence of degradation products.

Effect of cetyltrimethylammonium bromide on the electrochemiluminiscence and electrooxidation of luminol

1983 ◽  
Vol 48 (2) ◽  
pp. 477-483 ◽  
Author(s):  
Jan Lasovský ◽  
František Grambal
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Linear Sweep Voltammetry ◽  
Critical Micellar Concentration ◽  
Peak Height ◽  
Anodic Peak ◽  
Alkaline Solutions ◽  
Platinum Electrodes ◽  
Micellar Solutions ◽  
Linear Sweep ◽  
Low Concentrations

The electrooxidation of luminol in alkaline solutions in the presence of cetyltrimethylammonium bromide (I) was studied by linear sweep voltammetry on fixed and vibrating platinum electrodes. The presence of I in low concentrations (below the critical micellar concentration) brings about aggregation of the luminol, which is manifested by an increase in the anodic peak height and its shift towards lower potentials. In micellar solutions the peak height decreases owing to the slower diffusion of the bulkier micelles, the shift to lower potentials being preserved. The light-voltage curves correspond with the voltammetric curves, exhibiting identical shifts of the peak potentials in dependence on the concentration of the surfactant.

Sign in / Sign up

Export Citation Format

Share Document